Add counting sort.

Author: trekhleb

README.md

@@ -217,13 +217,13 @@ Below is the list of some of the most used Big O notations and their performance
 
 ### Array Sorting Algorithms Complexity
 
-| Name                  | Best      | Average   | Worst         | Memory    | Stable    |
-| --------------------- | :-------: | :-------: | :-----------: | :-------: | :-------: |
-| **Bubble sort**       | n         | n^2       | n^2           | 1         | Yes       |
-| **Insertion sort**    | n         | n^2       | n^2           | 1         | Yes       |
-| **Selection sort**    | n^2       | n^2       | n^2           | 1         | No        |
-| **Heap sort**         | n log(n)  | n log(n)  | n log(n)      | 1         | No        |
-| **Merge sort**        | n log(n)  | n log(n)  | n log(n)      | n         | Yes       |
-| **Quick sort**        | n log(n)  | n log(n)  | n^2           | log(n)    | No        |
-| **Shell sort**        | n log(n)  | depends on gap sequence   | n (log(n))^2  | 1         | No        |
-| **Counting sort**     | n + r     | n + r     | n + r         | n + r     | Yes       |
+| Name                  | Best      | Average   | Worst         | Memory    | Stable    | Comments  |
+| --------------------- | :-------: | :-------: | :-----------: | :-------: | :-------: | :-------- |
+| **Bubble sort**       | n         | n^2       | n^2           | 1         | Yes       |           |
+| **Insertion sort**    | n         | n^2       | n^2           | 1         | Yes       |           |
+| **Selection sort**    | n^2       | n^2       | n^2           | 1         | No        |           |
+| **Heap sort**         | n log(n)  | n log(n)  | n log(n)      | 1         | No        |           |
+| **Merge sort**        | n log(n)  | n log(n)  | n log(n)      | n         | Yes       |           |
+| **Quick sort**        | n log(n)  | n log(n)  | n^2           | log(n)    | No        |           |
+| **Shell sort**        | n log(n)  | depends on gap sequence   | n (log(n))^2  | 1         | No        |           |
+| **Counting sort**     | n + r     | n + r     | n + r         | n + r     | Yes       | r - biggest number in sorted array |